World Ocean Day 2025: Get to know South Australia’s oceans and why they matter!

Sunday (June 8) is World Ocean Day, an opportunity to unite, celebrate and advocate for our oceans and a healthy climate.

South Australians know the value of our oceans. Our coastline sustains our state in so many ways - from the annual migration of whales calving in the Great Australian Bight, to a thriving fishing industry famous for world-class abalone and crayfish. Our pristine beaches attract thousands of locals and tourists who enjoy surfing, swimming, diving and fishing.

A healthy, thriving ocean benefits us all. Sadly, since March, a naturally occurring, harmful algal bloom has affected parts of South Australia’s coastline.

The bloom has caused discoloured water and foam along parts of Fleurieu Peninsula, Kangaroo Island and the southern coast of Yorke Peninsula.

It has affected various marine wildlife, including fish, sharks, rays, seahorses and other gilled species, with dead marine life washing up on beaches.

Experts believe there are 3 plausible contributing factors causing the bloom:

• A marine heatwave that started in September 2024 – with sea temperatures about 2.5°C warmer than usual – combined with calm conditions, light winds and small swells.
• The 2022-23 River Murray flood washing extra nutrients into the sea.
• An unprecedented cold-water upwelling in summer 2023-24 that has brought nutrient-rich water to the surface.

Government agencies continue to monitor the situation.

The impacts of the algal bloom further highlight the importance of our oceans and their role in sustaining life as we know it.

Get to know South Australia’s ocean

1. We don’t have one ocean but 3: The Southern, Indian and Pacific Ocean all meet and intermix off southern Australia, creating a dynamic environment that influences every aspect of our lives from the weather we experience, to the coastal environment we enjoy and the food we eat.
2. Warm water inputs: In the western portion of South Australia’s ocean waters, temperatures are influenced by a warm water current from Western Australia called the Leeuwin Current. These warm currents allow some highly mobile fish species, typically of tropical origin, to be observed in the Great Australian Bight.
3. Cold water inputs: The Great South Australian Coastal Upwelling System is responsible for bringing nutrient-rich cold water to the surface, creating phytoplankton blooms and providing key food sources for krill and sardines, which are, in turn, important food sources for whales and fish such as tuna.
4. Significant carbon sink: The Southern Ocean is a major carbon sink, absorbing more carbon dioxide than it emits. This helps mitigate the effects of climate change by reducing the amount of CO2 in the atmosphere.
5. Great Southern Reef: The Great Southern Reef stretches from WA to NSW and supports amazing marine biodiversity, much of which is found nowhere else on the planet. SA’s oceanic waters help supply nutrients, oxygen and food to the GSR, where you can find blue gropers, leafy see dragons, giant cuttlefish and a host of sharks and ray species. There is also an incredible variety of life growing on the GSR, including macroalgae, sponges, crustaceans, bryozoans, echinoderms and molluscs.
6. Marine parks: South Australian waters are protected by a network of 19 marine parks in state waters, and 7 Australian marine parks in Commonwealth waters. Marine parks are an important tool for conserving marine biodiversity.

Why are oceans important?

1. Climate regulation: The ocean absorbs approximately 30% of carbon emissions and generates more than half the planet’s oxygen, helping combat climate change.
2. Food source: It provides 15% of the animal protein consumed globally, essential for many populations.
3. Jobs and livelihoods: 3 billion people depend on the ocean for their livelihoods.
4. Economic development: The ocean economy is estimated to be worth trillions of dollars, driving significant economic growth.
5. Survival: A healthy ocean is crucial for our overall wellbeing and survival.

Why do oceans need to be saved?

Our oceans face significant threats due to a combination of human activities and environmental changes.

• Pollution, particularly plastic waste, is contaminating marine ecosystems and harming wildlife. It's estimated that 8 million metric tonnes of plastic enter the oceans annually, leading to deadly consequences for marine animals that ingest or become entangled in it.
• Overfishing is depleting fish populations faster than they can replenish, disrupting the balance of marine ecosystems and threatening food security for millions who depend on seafood as a primary protein source.
• Climate change is causing ocean temperatures to rise and sea levels to increase, which contributes to coral bleaching and the loss of vital coastal habitats.
• Additionally, the oceans are absorbing about 30% of the carbon dioxide emitted by human activities, leading to ocean acidification that affects shell-forming species and the broader marine food web.

These combined factors highlight the urgent need for global conservation efforts to protect our oceans and ensure their health for future generations.

How can I help protect our oceans?

To help protect our ocean, you can:

1. Reduce plastic use: Use reusable bags, bottles and straws to keep plastic out of the ocean.
2. Get involved in restoration: Get involved with restoration projects aimed at restoring ecosystems, such as mangroves for coastal protection or seagrass for carbon sequestration, helping to reduce ocean acidification. Check out your local council initiatives to get involved or explore the Department for Environment and Water’s volunteering options.
3. Clean up: Join beach or river clean-up events to remove rubbish from waterways.
4. Save water: Use less water to reduce runoff that can carry pollution to the ocean.
5. Learn and share: Educate yourself about marine life and share what you learn with friends and family to raise awareness. Join a snorkelling tour or become a citizen scientist.

For updates on South Australia’s algal bloom, visit the Department for Environment and Water’s website.

Looking for more? Discover how biodiversity helps address climate change.